Bis(3-tert-butylpyridine-κN)bis(4-tert-butylpyridine-κN)bis(thiocyanato-κN)cadmium

The asymmetric unit of the title compound, [Cd(NCS)2(C9H13N)4], consists of one CdII cation located on a centre of inversion, one thiocyanate anion, one 3-tert-butylpyridine ligand and one 4-tert-butylpyridine ligand in general positions. The tert-butyl group of the 4-tert-butylpyridine ligand is disordered over two sets of sites in a 0.25:0.75 ratio and was refined using a split model. The CdII cation is coordinated by six N atoms of four tert-butylpyridine ligands and two N-bonded thiocyanate anions within a slightly distorted octahedral coordination environment.


Thorben Reinert, Inke Jess and Christian Näther Comment
The structure determination of the title compound was performed as a part of a project on the synthesis and properties of new coordination polymers based on transition metal thiocyanates and and N-donor ligands (Boeckmann & Näther, 2010. Within this project we have reacted cadmium(II)thiocyanate with 4-tert-butylpyridine in water, which results in the formation of crystals of the title compound by accident. Apparently, the 4-tert-butylpyridine was contaminated with 3tert-butylpyridine to a degree that allowed the formation of a few single crystals.
In the crystal structure the Cd atoms are coordinated by six N atoms of four tert-butylpyridine ligands and two Nbonded thiocyanato anions in mutual trans orientation in a slightly distorted octahedral geometry ( Fig. 1 and Table 1).
The Cd···N distances range from 2.3005 (36) Å to 2.4025 (28) Å. It is also worth mentioning that so far no other compound containing 3-tert-butylpyridine has been reported in the CSD.

Experimental
The title compound was obtained accidently during the reaction of 34.3 mg Cd(NCS) 2 (0.15 mmol) with 88.8 µl 4-tertbutylpyridine (0.60 mmol) in 1.50 ml water at RT in a closed 3 ml snap cap vial. After two weeks colourless needles of the title compound were obtained.

Refinement
The H atoms were positioned with idealized geometry and were refined using a riding model with U iso (H) = 1.2U eq (C) (1.5 for methyl H atoms) of the parent atom using a riding model with C-H = 0.95 and 0.98 Å. The tert-butyl group of the 4-tert-butylpyridine ligand is disordered and was refined using a split model with fixed site occupation factors of 0.75 and 0.25. The distances between the methyl groups in the two disordered moieties were restrained to be equal.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (